Add support for CSSValue->CSSSimpleLength when it is a percentage.

third_party/WebKit/Source/core/css/cssom/CSSSimpleLength.cpp

Index: third_party/WebKit/Source/core/css/cssom/CSSSimpleLength.cpp
diff --git a/third_party/WebKit/Source/core/css/cssom/CSSSimpleLength.cpp b/third_party/WebKit/Source/core/css/cssom/CSSSimpleLength.cpp
index 286446a87e2032af64fdd2ca8c986b0c96888c46..9596121a6671e1aa3a30ff8c3a2279a74a911be8 100644
--- a/third_party/WebKit/Source/core/css/cssom/CSSSimpleLength.cpp
+++ b/third_party/WebKit/Source/core/css/cssom/CSSSimpleLength.cpp
@@ -23,7 +23,9 @@ CSSSimpleLength* CSSSimpleLength::create(double value, const String& type, Excep
 
 CSSSimpleLength* CSSSimpleLength::fromCSSValue(const CSSPrimitiveValue& value)
 {
-    DCHECK(value.isLength());
+    DCHECK(value.isLength() || value.isPercentage());
+    if (value.isPercentage())
+        return new CSSSimpleLength(value.getDoubleValue(), CSSPrimitiveValue::UnitType::Percentage);
     return new CSSSimpleLength(value.getDoubleValue(), value.typeWithCalcResolved());
 }
 
@@ -32,6 +34,13 @@ bool CSSSimpleLength::containsPercent() const
     return lengthUnit() == CSSPrimitiveValue::UnitType::Percentage;
 }
 
+String CSSSimpleLength::unit() const
+{
+    if (lengthUnit() == CSSPrimitiveValue::UnitType::Percentage)
+        return "percent";
+    return CSSPrimitiveValue::unitTypeToString(m_unit);
+}
+
 CSSLengthValue* CSSSimpleLength::addInternal(const CSSLengthValue* other)
 {
     const CSSSimpleLength* o = toCSSSimpleLength(other);